Operating gear for adjustable propeller blades



Aug. 29, 1944. P. w. SEEWER OPERATING GEAR FOR ADJUSTABLE PROPELLER BLADES 2 Shets-Sheet 1 Filed Aug. 13, 1943 Aug. 29, 1944. I w, s w 2,357,229-

OPERATING GEAR FOR ADJUSTABLE PROPELLER BLADES Filed Aug. 15, 1943 v 2 Sheets-Sheet 2 {w M v I I Patented Aug. 29, 1944 OPERATING GEAR FOR ADJUSTABLE PR/OPELLER BLADES Paul Werner Seewer, Rugby, England, assignor to The English Electric Company Limited, London, England, a British company Application August 13, 1943, Serial No. 498,559 In Great Britain August 21, 1942 1 Claim.

This invention relates to water turbine and pump'rotors and to marine and aeroplane propellers which are provided with swivelling blades angularly adjustable, either automatically or by hand, while the rotor is in motion and more particularly to the operating gear for adjusting the blades. While propeller rotors of this type are in rotation, th forces acting on each blade are usually of considerable magnitude so that they can be overcome and controlled only by powerful fluid pressure servo-motors and connecting mechanisms.

The invention makes use of a hydraulic servomotor, a crank substantially rigid with each swivelling blade and operative connections directly between each crank and the servo-motor, these connections being disposed to transmit to the cranks a blade-swivelling force in a direction at a considerable angle to the axis of the rotor. In the arrangement according to our co-pending patent application No. 434,628 the servo-motor is furthermore an axially reciprocating servomotor inside the rotor in combination with a member reciprocable with, or as a part of, the

servo-motor having therein a plurality of grooves inclined at an angle to the axis of the rotor and a cooperating slider block pivotally mounted on the end of each crank. The sides of th slider block conform substantially to the sides of the grooves in the axially reciprocating member and are a sliding fit therein, this ensuring that the force transmitted from the reciprocating member to the slider block and hence to the crank is distributed substantially over engaging surfaces on th reciprocating member and on the slider block. In the arrangement described and illustrated in our said prior patent application No. 434,628 the slider block is flat sided and the groove is a correspondingly fiat sided channel.

The present invention. consists in the modification of that according to our co-pending patent application No. 434,628 wherein the said slider block and the groove or channel in which it slides are of circular arcuate formi. 'e., the slider block is a sector of a cylindrical ring and the groove in the reciprocating member is a channel .of the same shape. It is found that this has certain advantages in reducing the variation of the leverage at which the force applied to the reciprocating member acts on the crank with change of position of the reciprocating member and hence in reducing thevariation of the force required to be exerted by the servo-motor with change of position of the blades. It is an essential condition that firstly the surfaces of the side faces of the slider block should substantially conform to the surfaces of the side races of the grooves and that secondly the block should be a sliding fit within the groove; there are, however, only two possible shapes fulfilling these conditions, viz: the grooves and the block must have either straight flat sides as described in the said application No. 434,628 or they must be of circular arcuate form in accordance with the present invention.

The invention is illustrated by the accompanying drawings of which Fig. 1 is a vertical cross section through the rotor axis of a swivelling bladed hydraulic turbine incorporating the invention, Fig. 2 is a part diagrammatic view showing a prismatic grooved reciprocating member together with the slider block and the crank which actuates one of the swivelling blades, Figs. 3, 4 and 5 are diagrams showing three positions of the crank when the slider block and groove are straight-sided, while Figs. 6, 7 and 8 are corre-' sponding diagrams showing three positions of the crank when the slider block and grooves are of circular arcuate form according to the present invention.

As shown in Fig. 1, each swivelling turbine blade I is formed integrally with its spindle la and with an operating crank lb depending therefrom. The spherical hub 2a of the rotor incorporates bearings for the spindles l a. Each spindle is provided with an inner and an outer bearing, each crank being located between the two bearings, of which at least the outer bearings are split along a horizontal plane through the axes of the spindles la so that the single piece blades and cranks can be put in place and the bearings placed over them, the parts being spigotted into each other and held together by through-going bolts, screws or studs 4 with nuts and locking washers. The rotor is completed by the hood ll secured to the hub 2a and which may terminate in a separate nose [3 and is closed by the manhole cover l4.

Pivotally mounted on the lower end of each crank lb is a block 5 slidably fitting in a groove 6a in one face of a hollow prismatic member 6 disposed around the axis of the hub. For an eight-bladed rotor, for example, the prismatic member 6 is octagonal.

The prismatic member 6 is hollow with a cylindrical interior serving as the cylinder of the axial servo-motor and slidable on the fixed piston 9 carried at the lower end of a hollow part 21) of the hub (forming the piston rod) depending from the inner bearings. The member 6 has it upper boss 6b bored to fit slidably on the upper part of the piston rod; the lower end of the cylinder is closed by the cover It through which passes however the inner pipe l6 reciprocable with the servo-motor and serving to supply lubricating oil to the rotor interior. The stationary pipe l5 surrounding pipe 16 and secured to the piston 9 can supply fluid under pressure through the piston to the cylinder below the piston while the space between pipe I! and the inner wall of the turbine shaft 2| can supply fluid under pressure to the space above the piston. The cylinder 6 carries a diametrically opposite pair of projections 60 which engage and can slide axially between channelled guide members Ila projecting inwardly from the wall or the hood I l.

The arrangement thus far described is in accordance with the parent patent application No. 434,628 but in the parent application the slider blocks I are straight flat sided blocks sliding in corresponding straight grooves 6a formed in the faces of the prismatic member 8 at an acute angle to the axis oi. the hub. The admission of fluid under pressure to the servo-motor cylinder on one side or the other of the piston causes axial reciprocation of the member 6 and this imparts a swivelling movement to the cranks lb (and hence to the blades I) through the sliders 5 and the inclined grooves Ia.

The line of action of the force acting on the end of each crank lb is normal to the side face of the groove 6a and is accordingly inclined at an angle to both the horizontal and the vertical. The eflective leverage is accordingly the perpendicular distance from this line to the blade axis. It will be seen from Figs. 3, 4 and 5 how this perpendicular distance and hence the eifective leverage vary for diflerent position of the crank and blade, when the slider blocks and grooves are flat-sided in accordance with the parent patent application. If the crank arm-- 1. e., the straight line passing perpendicularly through the crank axis and the pivotal axis of 2,357,929 7 the slider blockwere parallel to the sides of straight-sided grooves, the sliding movement relatively to these grooves would be reduced to a minimum but there would still be an appreciable change of leverage. Space conditions, however, usually make this impossible. Fig. 2 shows the member 6 with curved grooves 6a and corresponding slider blocks 5 according to the present invention while Figs. 6, 7 and 8 show how, with these grooves 6a and blocks I bounded by cylindrical arcuate sides struck about an axis (through point A) parallel to but not coinciding with the pivotal axis of the crank the variation in the leveragei. e. in the perpendicular distance from the blade axis to a straight line normal to the cylindrical arcuate surfaces and passing through the pivotalaxis of the slider block-is les with the arrangement according to the present invention than with straight flat sided blocks and grooves.

What I claim as my invention and desire to secure by Letters Patent is:

A swivelling propeller bladed rotor comprising a hub, bearings incorporated therein, a plurality of swivelling propeller blades mounted in said bearing and projecting from said hub, a crank inside the rotor substantially rigid with each swivelling blade and extending therefrom, in one of its working positions, parallel to the rotor axis, a slider blo'ck pivotally mounted on the end of each of the said cranks and a member reciprocable axially within said hub having therein a plurality of curved channels, one per crank, extending obliquely across the said member, the sides of said channels being cylindrical arcuate surfaces struck about an axis parallel to but not coincident with the pivotal axis of the crank and appearing of concave form when viewed from the axis of the crank while the said slider blocks have arcuate sides conforming to and a sliding fit within said channels.

HAUL WERNER SEEWER. 

